Add composer.json with phpspec into project.
Add register customer use case specification
Add interface to be able to implement RegisterCustomer
Add basic implementation register customer.
Add specyfication for create and save user.
Add save to interface.
Implement save of user in user repository.
Add classic TDD example of value object.
Add example specs.
Add calculator simple example.
Merge remote-tracking branch 'origin/master'
Fixed readme.